The invention relates to an apparatus for removing deposition material residue that collects on the lower surface of the muffle in a gas blanketed down-flow type chemical vapor deposition reactor used in the fabrication of semiconductor devices.
Semiconductor devices typically include patterned layers of electrically conductive, non-conductive and semi-conductive materials stacked over a silicon wafer. The various layers of material are successively deposited on the wafer and etched into predefined patterns to form individual component structures within the particular device being fabricated. Chemical vapor deposition (xe2x80x9cCVDxe2x80x9d) reactors are commonly used for depositing layers of material by introducing select reactant gases into a controlled environment surrounding the wafer. One type of CVD reactor, referred to herein as a gas blanketed down-flow reactor, introduces the reactant gases downward through vertical channels over a wafer positioned horizontally beneath the channels. One such CVD reactor are the Watkins Johnson Company Models WJ-996, WJ 999R 3.3 and WJ 999R 3.5. In this type of CVD reactor, a conveyor belt moves the wafers through an elongated box like chamber called a xe2x80x9cmuffle.xe2x80x9d The conveyor belt travels along and is supported by the lower surface of the muffle. Multiple chemical vapor deposition chambers are located within the muffle. A modular gas injector assembly is positioned at each deposition chamber. The gas injector assembly introduces reactant gases into the deposition chamber. The wafers on the conveyor belt travel through each deposition chamber wherein the surface of the wafer is exposed to the gases and coated with the desired materials. Each gas injector assembly includes an array of plenums and passageways for properly mixing and directing the gases to the surface of the wafers. The injector assemblies also include exhaust ports for removing chemical vapors from the deposition chamber.
During the deposition process, deposition material residue collects on the conveyor belt and on the lower surface of the muffle within the deposition chambers. The residue is continuously removed from the conveyor belt by passing the belt through an etching station outside the muffle. Excessive residue build-up on the lower surface of the muffle can cause the conveyor belt to move unevenly through the deposition chambers, thereby adversely affecting the uniformity of the materials deposited on the surface of the wafers. Consequently, the reactor is periodically shut down to remove the residue that has collected on the lower surface of the muffle. During this shutdown, the conveyor belt is removed from the muffle and the gas injector assemblies are replaced with etch injector assemblies. Presently, so far as applicant is aware, etch injector assemblies for gas blanketed down-flow type reactors such as the Watkins Johnson models noted above are constructed to introduce a vaporized etchant into the deposition chamber and on to the exposed lower surface of the muffle to etch away the deposition material residue. In order to reduce the time necessary to clean the muffle and thereby minimize the time the reactor is out of production, it is desirable to use a liquid etchant to remove the residue from the muffle. The present invention is directed to the etch injector assembly that allows for the introduction of a liquid etchant into an etch chamber and on to the lower surface of the muffle to more rapidly remove deposition material residue from the muffle.
Accordingly, it is one object of the invention to introduce a liquid etchant directly on to the lower surface of the muffle of a gas blanketed down-flow CVD reactor during maintenance operations to remove deposition material residue that has collected on the lower surface of the muffle.
It is another object to provide a sealed and self-contained etch chamber for use with a liquid etchant.
It is a further object to provide a modular etch injector assembly adapted to replace modular gas etch injector assemblies used in gas blanketed down-flow CVD reactors during such maintenance operations.
These and other objects are achieved by a novel modular muffle etch injector assembly for use in a gas blanketed down-flow chemical vapor deposition apparatus of the type having a muffle and a modular gas injector assembly for introducing chemical vapors into a deposition chamber, the muffle being adapted for receiving and supporting the gas injector assembly, wherein deposition material residue collects on a lower surface of the muffle. The etch injector assembly of the present invention comprises an etch chamber having vertical sidewalls, a closed top end and an open bottom end, a supply mechanism for introducing a liquid etchant into the etch chamber, and a sealing device disposed along the open end of the etch chamber for providing a seal between the etch chamber and the lower surface of the muffle to confine the etchant to the etch chamber. The etch injector assembly preferably also includes an exhaust means for removing chemical vapors from the etch chamber. The etch injector assembly is adapted to replace the gas injector assembly within the deposition chamber during maintenance operations for removing the residue from the lower surface of the muffle by introducing the liquid etchant into the etch chamber and on to the lower surface of the muffle.
In another aspect of the invention, the etch injector assembly comprises a box-shaped etch chamber having a rectangular cross section and being open at its bottom end. The etch chamber is characterized by opposing sidewalls, opposing endwalls extending between the sidewalls, and a top cover plate attached to the sidewalls and endwalls. Inlet and exhaust ports are formed in the cover plate. The liquid etchant is introduced into the etch chamber through the inlet port. Chemical vapors are removed from the etch chamber through the exhaust port. A sealing device such as an xe2x80x9cOxe2x80x9d ring is positioned along the bottom surfaces of the sidewalls and endwalls for providing a seal between the open end of the etch chamber and the lower surface of the muffle to confine the etchant to the etch chamber. The etch injector assembly is sized and shaped to replace the gas injector assembly during maintenance operations for removing the residue from the lower surface of the muffle by introducing the liquid etchant into the etch chamber and on to the lower surface of the muffle.
Additional objects, advantages and novel features of the invention will be set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.